Patent literature 1: JP 2013-001152 A (corresponding to US 2012/0312604 A)
For example, Patent literature 1 discloses a vehicular occupant determination apparatus which determines a type of an occupant on a vehicle seat in order to operate an occupant protection apparatus such as an airbag apparatus, a seatbelt pre-tensioner. In order to determine whether the occupant protection apparatus operates or not, this kind of the occupant determination apparatus determines which situations including a case where (i) there is nothing on a vehicle seat (also, referred to as a vacant seat, or vacant), (ii) a child restraint systems (also referred to as a car seat) is leashed, (iii) a small-sized adult has a seat, or (iv) a large-sized adult has a seat. Hereinafter, by including the above situations regarding the vehicle seat determined by the occupant determination apparatus, the situations are named as a type of an occupant (hereinafter, also referred to as an occupant type).
In an occupant determination apparatus disclosed conventionally, a pair of front and rear load sensors is provided at a left-side support portion of the vehicle seat. And, based on a detection value of the load sensors, the occupant type on the vehicle seat is determined. In addition, the occupant determination apparatus determines the occupant type only when the detection value of an acceleration sensor which detects an acceleration of a lateral direction (also referred to as a vehicle width direction) of a vehicle is equal to or less than a predetermined threshold. That is, in a vehicle, the determination of the occupant type is not performed when the acceleration in the vehicle width direction exceeds the threshold. An occupant position or an occupant posture on the vehicle seat may change when acceleration occurs in the vehicle width direction according to a turning driving of the vehicle or the like. In this case, although the occupant type on the vehicular sheet has not changed, it may be determined that the occupant type has changed. According to a conventional occupant determination apparatus, a wrong transition of a determination result of the occupant type due to the acceleration generated in the vehicle width direction can be prevented.
The inventors of the present application have found the following regarding a conventional occupant determination apparatus. According to the conventional occupant determination apparatus, the occupant type is not determined when the acceleration in the vehicle width direction exceeds a threshold. Thus, when the occupant type on the vehicle seat has changed in actual, the determination of the occupant type may be delayed. Especially, there may be a case where the determination result of the occupant type transits (changes) to a proper determination result with taking a time during driving of the vehicle after the occupant determination which is different from an actual occupant type has been made. Further, there may be a case where the occupant has a seat or leaves a seat in the vehicle during driving. In the cases, the determination result of the occupant type may be required to transit even though the acceleration in the vehicle width direction occurs. The determination of the occupant type, which is different from the actual occupant type, may remain until the vehicle drives a straight road or stops in a flat road, when the determination result of the occupant type does not transit due to the occurrence of the acceleration,